Google has been rolling out monthly updates to their Nexus line of devices - which also includes the Pixel C. The May 2016 update, which patched a slew of security issues, has been more of a headache for some Pixel C owners, than anything else. Some users are reporting that the Pixel C is randomly rebooting after this latest over-the-air update. It appears to be happening anywhere from every five minutes to every thirty minutes, when the tablet is not plugged in. As you can guess, this is becoming quite the headache for most Pixel C users.
It appears that the issue has to do with a power-saving feature on the Pixel C. As the random reboots are only happening when the tablet isn't being actively used. It's tough to say whether this is an issue with Doze or not, considering it's only happening with the Pixel C - so far. It's also worth noting that those with the Android N Developer Preview have had the same issue. But since it was a developer preview, many likely figured it was just an issue with having early, unfinished software. It seems that flashing back to the April update - that's build M5C14J - has fixed the issue for Pixel C users affected by the issue. On that note, it's also worth mentioning that not every Pixel C user on the May update (build MXC89F) is having the random reboot issue. But it also isn't an isolated issue.
As you'd expect, the issue has been posted on the Google Product Forums and the Android bug tracker. Although there has yet to be an official response from Google just yet, they should be aware of the issue. Hopefully we'll see a fix for this issue in the June 2016 security update, along with all of the other security vulnerabilities that will be patched as well.
The Pixel C is Google's high-end Android tablet, it was actually built in-house. Unlike the Nexus tablets that we've had in recent years. Those were built by their hardware partners - HTC, ASUS and Samsung. The Pixel C is also going to play a pretty big role in the Android N launch, seeing as their big feature is multi-window, and that works great on the Pixel C's aspect ratio.